Sclerocoelus aduncus, Kuwahara & Marshall & Paiero, 2025

Kuwahara, Gregory K., Marshall, Stephen A. & Paiero, Steven M., 2025, A revision of the genus Sclerocoelus Marshall (Diptera: Sphaeroceridae), European Journal of Taxonomy 979, pp. 1-277 : 22-23

Sclerocoelus aduncus sp. nov.

urn:lsid:zoobank.org:act:C599DCDE-8989-4D4E-927C-A00C7A4134B4

Figs 5A, 11–12

Etymology

This name refers to the apically hooked male cercus (from the Latin ‘ aduncus ’, meaning ‘hooked, bent, curved’).

Material examined

Holotype

ECUADOR • ♂; Pichincha, Campamento Pichan, near Nono ; 3350 m a.s.l.; 0°7′31″ S, 78°33′56″ W; 24 Oct. 1999; S.A. Marshall leg.; cloud forest, green leaf litter; QCAZ debu00115508.

Paratype

ECUADOR – Pichincha • 1 ♂; same data as for holotype; DEBU debu00115545 .

Description

BODY ( Fig. 11A). Length 2.9–3.4 mm. Head dark brown, orbital plate, face, and antenna orange; gena and frontal vitta reddish. Frontal width 2.2–2.3 × frontal height. Two pairs of large interfrontal bristles surmounting a fine third (holotype has a third large interfrontal bristle on one side); anterior orbital 0.4– 0.5× length of posterior. Palpus pale brown. Eye very large, greatest height about 5.0 × shortest genal height. Thorax dark brown, scutum shiny with slightly paler lateral edges. Two pairs of dorsocentral bristles (anterior pair distinct, 0.4× length of posterior pair) separated by 5–6 rows of acrostichal setulae. Membrane around prosternum bare. Legs dark brown, foreleg paler. Fore femur with four large ventral preapical setae. Dorsal surface of mid tibia with a small pair of setae at ¼, a large anterior seta just above ½, and a large pair of setae at ¾. Ventral surface of male mid tibia with two rows of stout setae along apical third. Wing ( Fig. 5A) short, extending only to midpoint of T3; strongly infuscate. All veins distinguishable. CS2 0.6–0.7 × CS3. Halter reduced to a small white nub.

MALE ABDOMEN ( Figs11B–C, 12).Dark brown,posterior edges of tergites sometimes slightly desclerotized. T2–5 and S2–4 uniformly long-setose with large posterolateral setae. S5 broad, rectangular, 0.9× length of S4, broadly desclerotized posteromedially, setae largely restricted to desclerotized area. Anterior flange of S6+7 not developed. Additional sclerites of genital pouch inconspicuously developed on anterior face of genital pouch (perpendicular to S5): sclerite A dark, fused to S6+7; sclerite B dark, arched into genital pouch; sclerite C apparently absent; sclerites D and E fused into a dark, posteriorly bilobed sclerite; sclerites F and G fused, dark with a rounded, preapical notch on left side; ring sclerite weakly sclerotized. Epandrium small, 0.7× length of S8, height 1.9× maximum length and 0.8× maximum width, densely setose; anal fissure small, ovoid; perianal pads weakly developed. Pseudocercus absent; halves of subepandrial sclerite broadly arched, thin, closely associated medially but not fused together. Cercus slightly sinuate in posterior view, curved with apex hooked, flattened and extended anteriorly. Hypandrium with anteromedial apodeme tapered and sinuate. Surstylus broad, subequal in length and height, subquadrate with dense ventral setae and a triangular anterobasal lobe. Postgonite with basal third boxy, apical two-thirds narrow, sinuate, apex emarginate with a slight anterior, preapical lobe. Phallapodeme narrow, slightly sinuate; basiphallus stout and connected to distiphallus by a neck-like distal part; distiphallus large with a downturned, tubular, sclerotized part and a large membranous, ventral part.

FEMALE ABDOMEN. Female unknown.

Distribution

Neotropical: Ecuador.

Remarks

Sclerocoelus aduncus sp. nov. is easily identified by the strongly reduced wing ( Fig. 5A) with a small alula (all other brachypterous species have a large alula), apically hooked male cercus, and small, subquadrate surstylus. Sclerocoelus aduncus has distinct cerci fused basally into a subanal plate but lacks separate pseudocerci or subcerci. These characters suggest that S. aduncus and the similarly brachypterous species S. flavus sp. nov., S. limbus sp. nov., and S. meridensis sp. nov. are among the few species in the genus that are basal to the large, derived groups characterized by separate subcerci and pseudocerci. All four species are associated with wet, green plant material in high elevation cloud forests or elfin forests in the Andes.